The present invention relates to air dryers. It finds particular application in conjunction with air dryers used on vehicles and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Air dryers are used, for example, on heavy vehicles for drying compressed air delivered from a compressor to a vehicle operating storage reservoir for use in operating various systems on the vehicle that utilize compressed air. One type of air dryer includes a cartridge, which includes a desiccant material through which the compressed air passes while being dried. The cartridge is secured to an air dryer housing.
As the compressor provides air during a charging cycle, the desiccant becomes saturated with moisture and other contaminants that are removed from the compressed air. At the end of the charging period, the air dryer is switched into a regeneration mode during which previously dried compressed air is purged from a regeneration storage volume and, furthermore, passes through the desiccant material. As the air from the regeneration volume passes through the desiccant, the moisture and contaminants in the desiccant are captured in the airflow and, furthermore, removed from the desiccant. The air including the moisture and contaminants is then expelled (e.g., exhausted) from the air dryer.
Although the desiccant is frequently regenerated in the manner described above, it is to be understood that the desiccant degrades over time due to the presence of contaminants (e.g., oil) in the incoming air stream. In fact, more and more residual oil and contaminants can be retained in the desiccant after each regeneration cycle. Therefore, over time, the desiccant becomes oil saturated such that it cannot be satisfactorily regenerated by the regeneration cycle described above. Although the life of the desiccant may be extended by improved purge functionality, at some point, the desiccant must be replaced.
Since dried compressed air from the previous charge cycle is used for purging the desiccant, it is to be understood that it is desirable to store the driest and cleanest air from that charge cycle in the regeneration storage volume. Because regeneration with wetter air is not as effective, it is, therefore, desirable to store the first air passing through the desiccant in the regeneration storage volume. In this case, the first air dried and cleaned by the desiccant is stored in the regeneration storage volume and, furthermore, is used for regenerating the desiccant. None of the cartridges currently known includes any means for serially directing the first air that passes through the desiccant after the regeneration mode into a regeneration storage volume prior to filling the vehicle operating storage reservoir. Therefore, none of the currently known cartridges results in the driest air being used to regenerate the desiccant during the purge cycle for more effectively recharging the desiccant.
One further advantage of including the desiccant within the cartridge is that the desiccant can be easily replaced by swapping the original cartridge for a new cartridge, which includes new desiccant. However, until now, there has not been a cost-effective way of replacing the oil fouled desiccant in a spin-on cartridge with fresh desiccant so that the cartridge can be reused.
Also, current air dryer designs typically include a flat load plate on the bottom. Because of high stresses directed on the load plate, the load plate tends to require higher thickness (e.g., at least about ¼″ thickness) to prevent warping and/or failure.